Electric switch



Aprll 5, 92 J WHALEN ELECTRIC SWITCH Filed Dec. 26. 1924 Patented Apr.5, 1927. 4

PATENT OFFICE.

JAMES WHALEN, OF OMAHA, NEBRASKA.

ELECTRIC SWITCH.

Application filed December 26, 1924. Serial No. 758,186.

My invention relates to electric switches of the class in which one ormore poles of the switch consist of conductive fluid or metal such asmercury. It is the object of my invention to provide a switch especiallydesigned and adapted for 'use with electric motors as a safety device orautomatic cutout for stopping the current supply to the motor when thelatter is overloaded to such an extent and for such time as to causeheating thereof to a predetermined temperature, whereby the motor may beprotected from overheating, independently of the current values of theelectrical supply thereto. A further object of my invention is toprovide a switch capable of opening or breaking a circuit in which aheavy current is flowing, without causing arcing at theswitch-poles,'and in which the moving parts of the switch mechanism areso constructed and arranged as to be operable with a very smallexpenditure of energy. A further object is to provide a switch employingas one of the separable poles a body of fluid metal or amalgam of suchcomposition as to have no appreciable solvent action upon the solidmetal poles or other parts with which the fluid is in contact. A furtherobject of my invention is to provide a switch wherein the separation ofpoles takes place beneath the surfaceof a body of non-conductive liquidwhich serves to inhibit arcing, and in which said liquid is transparentand is retained within a transparent container, whereby the action maybe observed if desired. A further object is to provide a switch of thecharacter above set forth, in

which the parts are biased to circuit-opening position and are held incircuit-closing position by a trigger device, the latter beingsufliciently sensitive to readily enable its operation by directmechanical connection with a thermostatic element.

In the accompanying drawings Fig. 1 is a side view of a switch embodyingmy invention, Fig. 2 is a longitudinal vertical section of the same,Fig. ,3 is an end vieW thereof, Fig. 4 is a vertical section on the line4-4 of Fig. 2, and, Fig; 5 is a detail section on the line 5-5 of Fig.2.

In carrying out my invention according to the illustrated embodimentthereof, I

provide a fixed frame comprising the metal end-members 10 and 11 ofwhich the lower parts or legs are'connected by longitudinal rods 12, andthe upper ends are connected to each other by a bar 13 of insulatingmaterial. In the end-members 10 and 11 are secured the insulatingbushings 14 and 15. The bushing 14 is bored to form a bearing for thereduced end 16 of a shaft 17. The opposite end of the shaft is threaded,and upon said threaded portion is screwed the sleeve-nut 18 to which issecured the handwheel 19, the latter being of insulating material. Thesleeve-nut 18 extends through the bushing 15, being rotatable therein sothat said bushing forms a bearing for the shaft 17, of which the member18 may be regarded as an extension. Adjoining the reduced end 16 of theshaft, a collar 20 is secured thereon by sweating the parts together,said collar having an annular flange 21- extending toward the bushing 14and inclosing a cylindrical space about the shaftend 16. In said spaceis disposed the spring 22 of which one end is connected with the shaftand the other to the bushing 14, the spring being under a tensiontending to rotate the shaft in the direction of the arrows A in Figs. 3and 4. A pin 23 on the bushing 14 extends into a notch in the end of theflange 21, the circumferential extent of said notch being such thatrotation of the shaft is limited to about one-fourth of a revolution. Onthe shaft 17, between the collar 20 and the inner end of the sleeve-nut.18, is disposed a cylinder or drum which is constructed as follows: Apair of sleeves 24 and 25, of insulating material, each having anintegral flange at one end, are disposed upon the shaft so. that theflanged ends adjoin respectively said collar 20 and sleevenut 18. Uponsaid sleeves 24 and 25 are mounted the metal end-pieces 26 and 27 of thedrum or cylinder, and between said endpieces is disposed the tube 28which is preferably of glass, the ends of said tube fitting inside theperipheral flanges of the endpieces and seating against gaskets 29 whichinsure fluid-tight joints between the tube and the end-pieces. Thesleeves 24 and 25 fit tightly upon the shaft 17 to form fluid-tightjoints therewith, but are slidable longitudinally of the shaft to theextent necessary for transmitting the clamping pressure from thesleeve-nut 18 tothe collar 20, whereby to press together thedrum-members 26, 27

liquid 32, sufficient to fill the remainder of the drum-space to a levelapproximately as shown, the un-filled air-space at the top being of suchvolume as to allow for the thermal expansion of the contained liquidswithout causing more than a nominal increase of pressure within thecylinder. The fluid metal 31 is preferably an amalgam formed bydissolving in mercury a quantity of ordinary soft solder (consisting ofequal parts by weight of lead and tin) as much as the mercury willdissolve without loss of active fluidity at ordinary temperatures. Theuse of such an amalgam instead of pure mercury is preferred for thereason that it is desirable to employ for the end-pieces of the drum,the shaft 17, and contact-piece" 30, metal of high electrical.conductivity, such as copper, which is soluble or amalgamable'to aconsiderable extent by pure mercury, but which I have discovered to benot soluble or amalgamable to an appreciable degree in the describedmercurysolder amalgam; so that by the use-of the, am the parts namedmay-be of fluid a'mal copper wit outsuifering depreciation ,undercontinued use in contact with the fluid conductor. .The amalgam is alsoless 'ex-,

pensivethan pure mercury. The liquid 3.2 is preferably glycerine, ofwhich the insulating properties are sufficient to effectively suppressarcing, and which. being transparent, enables observation of the immersed parts when desired.

On the insulating frame-bar 13 are mounted a pair of binding-posts 33 towhich are connected the terminals of the circuit to 'be controlled bythe switch. From said binding-posts 33 the flexible conductors 34 areextended to collars 35 and 36, said collars being secured respectivelyto .the collar 20 and to the hub of the end-piece 27 of the drum. Thedrum and shaft are revoluble' as a unit, the shaft-end 16 turn ingwithin the bushing-14, and the shaft" extension or sleeve-nut 18'turning within the bushing 15. When the drum and shaft are positioned asshown in Figs. -1, 2 and 4, so that the contact-sector 3O dips into thefluid metal 31, the electric circuit is closed through the,binding-posts 33 conductors-34, collars 35 and 36, drum end-piece '27,amal gam 31, contact-sector 30, shaft 17, and collar 20. When the shaftand'drum are rotated 50 that the contact-sector 30 extends laterally ina position such as indicated by dotted lines in Fig. 4, the circuit isopened between the amalgam and said contact-sector.

In the illustrated structure, rotation of the drum and shaft to thecircuit-opening position ,is effected by the spring 22, of which thetension serves to bias the switch to said circuit-opening position. Forretaining; the switch in circuit-closing position the following meansare provided: On the end-piece 27 is revolubly mounted a roller 37 ofinsulating material, a pin or stud 38 being attached to the member 27for carrying said roller. On, the adjacent frame-member 11 is pivotallymounted a. trigger or lever comprising an arm 40 which extends upwardlyfrom the pivot-pin 39 and has a curved terminal portion 41 of which theinner face forms a seat for the roller '37, and an arm 42 which extendsin hori zontally to a point beneath the axis of the drum-shaft 17. Thelever is so proportioned that when the roller is engaged with the curvedseat-portion 41 the pressure upon the lever, ,due to the attention ofthe spring 22 tending to rotate the drum as described, will be exertedalmost directly toward the lever-fulcrum or axis of the pivotpin 39, andthere will be no tendency for the roller-pressure to move the lever,although a very slight movement of the lever outwardly will enable theroller-pressure thereon to cause a further displacement or tilting ofthe lever about its fulcrum, whereby the roller may swing past the seat,and the drum thus be released and permitted to rotate to thecircuit-opening position.

Extending transversely between the framerods 12 is a rocking-shaft 43 ofwhich the ends are pivoted in said rods, and to the central portion ofsaid shaft is attached one end'of a thermostat-bar 44. Said bar extendsfrom the shaft longitudinally of the frame between the legs of theend-member 1Q, -and is then turned downwardly in a U-bend of which thelower portion passes Iback beneath the shaft, extending beyond the sameto a point below the arm 42 of the trigger-lever, and a terminal portion45 being turned upwardly to engage said arm 42. In the legs of the frameend-member 10 is journaled a small shaft 46 having upon the centralportion thereof a cam or eccentric 47 which engages the upper side ofthe bar 44. One end of the shaft 46 extends through the frame-leg andcarries a small graduated disk 48, a. fixed finger or pointer 49 beingextended out from the leg and terminating near the periphery of the diskas a reference point for reading the graduations' thereon. The cam oreccentric may be rotated by means of the shaft 46 to move the bar 44pivotally about the axis of the Said bar is adjusted to a position suchthat upon a. rise of temperature thereof to a predetermined degree theend portion will be raised sufliciently to slightly lift. the arm 42 ofthe trigger-lever, thereby tilting the vertical arm 40 outwardly to aposition at which the pressure of the roller 37 upon the curved seat 41will cause the further displacement required to permit rotation of theswitch-drum to the circuit-opening position. The current supply formotors of moderate size may be controlled directly by the switch, andfor motors requiring a very heavy current, or on ahigh-voltage circuit,the switch may be employed as a relay to control the current foroperatin a mamswit-ch controllingthemotor-circuit. In the described andillustrated structure the switch operates solely as a safety cut-out toprevent overload of the motor by opening the motor-circuit or acontrol-circuit, and the circuit is closed manually by turning thehand-wheel 19 to restore the drum to circuit-closing position, at whichit is held by the engagement of the roller with the seatportion of thetrigger-lever. The thermostatic device may be calibrated so that thegraduations on the disk 48 will indicate directly the temperatures atwhich the switch will be released, when the respective graduations areset at the pointer 49.

' It will be seen that the operation of the switch mechanism properrequires a movement only of the rigid unit comprising the drum,contact-sector and shaft, the liquid 31 and 32 remaining in asubstantially fixed position during the rotation of the drum..

The fixity of posit-ion of the liquids result both from thegravitational tendency thereof to remain in the lowermost portion of thecontainer, and from the inertia thereof, particularly of the heavyfluid-metal, resisting displacement of its position, so that the slightfrictional contact between the liquids and the drum is insufficient toeffect an appreciable movement of the liquids. Because of the smallamount of energy required to actuate the rotating unit, the latter maybe moved quite rapidly by the force of the biasing spring 22, althoughthe tension of said spring is very small. In consequence thereof, thetripping of the trigger-lever to release the switch may be effected soeasily that the. thermostatic device may be extremely sensitive. Therapid movement of the drum to circuit-opening position causes quickseparation of the polar elements, and the flow of the non-conductiveliquid into the polar space suppresses all arcing between the poles. Theliquid elements are protected against changes of composition or volumewhich might result from exposure thereof to atmosphere, said liquidsbeing substantially sealed within the drum by the clamping together ofthe drummembers.

Now, having I described my invention, what I claim and desire to secureby Letters Patent is:

1. An electric switch comprising a rotatable axially horizontallycylindrical drum having a conductive peripheral portion, a

contact-member inclosed by said drum and fixedly connected therewith andinsulated therefrom, means for connecting terminalsof an electriccircuit with said contact-member and the conductive portion of the drum,a body of fluid metal disposed within the drum and tending bygravitation and inertia to remain constantly in the lowermost portion ofthe drum during rotation thereof, said fluid metal being an amalgam ofmercury and solder, and means for rotating the drum to positions atwhich the contact-member is dipped into and withdrawn from the fluidmetal to respectively close and open the electric circuit.

2. An electric switch comprising a rotatable axially horizontalcylindrical drum having a conductive peripheral portion a contact-memberinclosed by said drum and fixedl connected therewith and insulatedtherei i om, means for connecting terminals of an electric circuit withsaid contact-member and the conductive portion of the drum, a body offluid metal disposedwithin the drum and tending by gravitation andinertia to remain constantly in the lowermost portion of the drum duringrotation thereof, means for rotating the drum to positions at which thecontact-member is dipped into and withdrawn from the fluid metal torespectively close and open the electric circuit, means tending to movethe drum to circuit opening position, a trigger having a seatportionmovable adjacent to the drum, and a member on the drum engageable withsaid seat-portion of the trigger to retain the drum in circuit-closingposition.

3. In an electric switch a body of fluid metal, a container in closingsaid fluid metal and shaped to enable said metal to remain substantiallyfixed in position during rot-aabout said fixed axis, means tending torotate the container in one direction, and a trigger device releasablyconnected with the drum for holding the same in a fixed position.

4. In an electric switch, a fluid-metal pole consisting-of an amalgam ofmercury and solder.

5. In an electric switch, a fluid-metal pole consisting of an amalgam ofmercury with lead and tin. 1

6. In an electric switch, a pole comprising a fluid mixture of mercuryand a metal not normally fluid.

7 In an electric switch, a pole comprising a conductive fluid formed bya comblnation of mercury with metal not normally fluid.

8. In an electric switch, a pole of fluid metal consisting of acombination of mercury amalgamated" with metal of higher electricconductivity than mercury alone.

9. In an electric switch, a pole consisting of 20 a fluid mixture ofmercury and metal of greater electrical conductivity than mercury alone.

JAMES VVHALEN.

